Evaluation of E-cigarette liquid vapor and mainstream cigarette smoke after direct exposure of primary human bronchial epithelial cells

Int J Environ Res Public Health. 2015 Apr 8;12(4):3915-25. doi: 10.3390/ijerph120403915.


E-cigarettes are emerging products, often described as "reduced-risk" nicotine products or alternatives to combustible cigarettes. Many smokers switch to e-cigarettes to quit or significantly reduce smoking. However, no regulations for e-cigarettes are currently into force, so that the quality and safety of e-liquids is not necessarily guaranteed. We exposed primary human bronchial epithelial cells of two different donors to vapor of e-cigarette liquid with or without nicotine, vapor of the carrier substances propylene glycol and glycerol as well as to mainstream smoke of K3R4F research cigarettes. The exposure was done in a CULTEX® RFS compact module, allowing the exposure of the cells at the air-liquid interface. 24 h post-exposure, cell viability and oxidative stress levels in the cells were analyzed. We found toxicological effects of e-cigarette vapor and the pure carrier substances, whereas the nicotine concentration did not have an effect on the cell viability. The viability of mainstream smoke cigarette exposed cells was 4.5-8 times lower and the oxidative stress levels 4.5-5 times higher than those of e-cigarette vapor exposed cells, depending on the donor. Our experimental setup delivered reproducible data and thus provides the opportunity for routine testing of e-cigarette liquids to ensure safety and quality for the user.

MeSH terms

  • Bronchi / drug effects*
  • Electronic Nicotine Delivery Systems / adverse effects*
  • Epithelial Cells / drug effects*
  • Humans
  • Nicotine / adverse effects*
  • Smoke / adverse effects*


  • Smoke
  • Nicotine